An improved rocker arm lubrication arrangement

Abstract: A rocker arm lubrication arrangement for an engine. The arrangement comprises a shaft (12) which pivotally mounts a number of rocker arms (40). The shaft (12) has a longitudinally extending lubricant supply bore (30) and radially upwardly extending supply bores (34) corresponding to positions of the rocker arms (40). Lubricant passes along the longitudinally extending supply bore (30) to the radially extending bores (34) and then exits via corresponding bores (52) in the rocker arms. The lubricant is under pressure and thus exits as jets of lubricant which impinge on an underside (72) of an engine cover (60) to be returned as a lubricant spray. The rocker arms may be arranged on the shaft (12) such that the jets are intermittent.

Description: The present invention relates to an improved rocker arm lubrication arrangement which is intended particularly, but not exclusively, for use in an internal combustion (i.c.) engine. Lubrication of a rocker arm assembly can be by means of an oil mist generated within an engine housing. The oil mist coats engine components lubricating any surfaces of contact between them. The mist may not reach into the upper regions of the housing below the engine cover. This can result in the metal to metal contacts at both ends of the rocker arms remaining dry leading to excessive wear and the need for frequent readjustment and replacement of parts. One solution to this problem has been to drill oil channels laterally through the bosses of the rocker arms. The channels each communicate at first ends with an oil supply passage in the rocker arm support shaft, which normally provides a supply of oil to lubricate rocker arm bushes, and which each exit at second ends at appropriate points on the rocker arm bodies to supply oil to the push rod ball joints and rocker arm ends contacting valve stem assemblies. This solution is expensive since the rocker arms are often formed of cast or forged metal and drilling of this material is difficult, particularly bearing in mind the narrow diameters of the drilled channels compared to their relatively long lengths. There is considerable wastage of rocker arms during the machining process due to broken drill bits, for example. A further problem is that the casting or forging tolerances must be closely controlled to ensure that the drilled holes run centrally down the bosses. A different solution is disclosed in FR-A-2 464 364. This discloses an internal combustion engine having an engine cover located above a rocker arm assembly comprising a rocker arm support shaft and a rocker arm pivotally mounted on the shaft. The cover member includes a deflector member for receiving a jet of lubricant rising from a supply bore in the rocker arm. The deflector member directs the lubricant to lubricate a contact between a hose end of the rocker arm and a revolving cam with which said hose end is in sliding contact. The deflector member is located above but to one side of the rocker arm and thus only a contact between one end of the rocker arm and a corresponding engine component is lubricated. It is an object of the present invention to obviate and mitigate the aforesaid problems and reduce machining time and hence cost. According to a first aspect of the present invention, there is provided a rocker arm lubrication arrangement comprising a rocker arm assembly consisting of a number of rocker arms mounted for pivotal movement about a longitudinally extending support shaft formed with a longitudinally extending lubricant supply bore and a number of radially upwardly extending lubricant supply bores communicating therewith, wherein at least one of said radially upwardly extending bores communicates with an upwardly extending lubricant supply bore in a corresponding one of said said rocker arms such that lubricant passing under pressure through said longitudinally extending supply bore to said upwardly extending supply bore forms a jet of lubricant which rises through said corresponding bore in the rocker arm to impinge upon an underside of an engine cover and to be directed to lubricate a contact between an end of the rocker arm and an engine component, characterised in that said at least one of the radially upwardly extending bores in the support shaft extends radially substantially vertically such that the jet of lubricant rises substantially vertically through the corresponding bore in the rocker arm to impinge upon the underside of the engine cover to be returned as a spray to lubricate contacts between opposed ends of the rocker arm and corresponding engine components. According to a second aspect of the present invention, there is provided a method of lubricating a rocker arm assembly comprising: providing an internal combustion engine including a rocker arm support shaft, a number of rocker arms pivotally mounted on the rocker arm support shaft, and an engine cover located above the rocker arm support shaft and the rocker arm; supplying lubricant under pressure along a longitudinally extending bore formed in the rocker arm support shaft; diverting the lubricant upwardly through a number of radially upwardly extending bores in the shaft and corresponding bores in the rocker arms to thereby form a jet of lubricant; impinging said lubricant jet on an underside of the engine cover to direct said lubricant to lubricate a contact between an end of the rocker arm and an engine component; the method being characterised in that the support shaft is arranged in the engine such that the upwardly extending bores in the support shaft are directed to extend radially substantially vertically and the jet of lubricant rises substantially vertically through the substantially vertically extending bores and the corresponding bores in the rocker arms to impinge on the underside of the engine cover to be returned as a spray to lubricate contacts between opposed ends of the rocker arm and corresponding engine components. According to a third aspect of the present invention there is provided an engine cover for an internal combustion engine, said cover being arranged to locate, in use, on an engine above a rocker arm assembly comprising a rocker arm support shaft and a number of rocker arms pivotally mounted on the shaft, said engine cover including a deflector member configured to receive a jet of lubricant rising out of a supply bore formed in the rocker arms and to direct said lubricant to lubricate a contact between an end of the rocker arms and a corresponding engine component, characterised in that the deflector member is positioned on said engine cover such that, in use, it locates at a position generally vertically above the rocker arm bore and it is configured to return the jet of lubricant as a spray for lubricating opposed ends of the rocker arms and corresponding engine components. The foregoing and further features of the present invention will be more readily understood from the following description of a preferred embodiment, by way of example thereof, and with reference to the accompanying drawings, of which: Figure 1 is a partially exploded perspective view, to a smaller scale, of a rocker arm assembly in accordance with the present invention; Figure 2 is an enlarged sectional view along line A-A of figure 1; Figure 3 is a side elevational view of a rocker arm in accordance with the present invention; Figure 4 is a sectional view along line B-B of figure 3; Figure 5 is a sectional view, to a reduced scale, along line C-C of figure 3; and Figure 6 is a side sectional view of an upper portion of an internal combustion engine illustrating a rocker arm lubrication arrangement in accordance with the present invention; Figure 7 is an enlarged view corresponding to the revealed portion of figure 1. Referring to the drawings, figure 1 shows a partially exploded perspective view of a rocker arm assembly 10 in accordance with the present invention. The assembly 10 comprises a longitudinally extending support shaft 12 upon which are mounted rocker arms 14 at predetermined positions along the length of the shaft 12. Adjacent pairs of rocker arms 14 are separated by pedestal blocks 16 which each essentially comprise a split collar type clamp. One pedestal block 16 has a location screw 18 which screw-threadedly engages a threaded hole 20 in an upper half 16' of the pedestal block such that an end of the screw 18 locates in a counter-bore (not shown) in the shaft 12 to angularly and axially position the shaft with respect to the block. The holes 20 in the other blocks are utilised to secure the engine cover. The pedestal block also has a locking screw 22 which extends through a hole 24 in its upper half 16' to screw-threadedly engage a hole in its lower half 16'' to enable the block 16 to be clamped upon the shaft 12. Between each pair of blocks are positioned two rocker arms 14, each of which abuts a respective block, and which are separated by a spring 26 mounted on the shaft therebetween. Screws 28 retain the end rocker arms and also plug the shaft bore. The rocker arm assembly is mounted upon the cylinder head and secured by screws through the pedestal blocks. The shaft 12 is formed with a longitudinally extending bore 30, which is better seen from the enlarged sectional view of figure 2. The longitudinally extending bore 30 of the shaft 12 extends the length of the shaft and communicates, for passage of lubricant, with a number of downwardly directed bores 32 and a number of upwardly directed bores 34, which will be explained in more detail later. In addition, a lubricant transfer means (figure 1) comprising a pipe member 36 and upper and lower sealing rings 38 locates in one of the downwardly directed bores 32 in order to supply engine lubricant at pressure to the bores (30,32,34) of the shaft 12. Each of the rocker arms 14 is located at a position on the shaft having a cross-section identical to that of figure 2. Figure 3 is an enlarged side sectional view of a rocker arm 14. The rocker arm comprises a rocker arm body 40 having a central bore 42 into which a bush bearing 44 locates and through which, in use, the support shaft 12 locates for supporting the rocker arm 14 for pivotal movement thereabout. The rocker arm 14 also has a machined nose portion 40' which, in use, contacts with a valve stem assembly 46 (figure 6). An opposing end 40'' of the rocker arm body 40 has an aperture through which an adjusting screw 48 extends, the adjusting screw being capped by a lock nut 50. The rocker arm also has a generally upwardly directed bore 52 formed in a top portion of the body 40 wherein said bore 52 communicates with the central bore 42 of the body via an aperture 45 in the bush 44. In accordance with the present invention, it is important that the bush 44 is located into the central bore 42 of the rocker arm body 40 such that the aperture 45 in the bush is aligned with the upwardly directed bore in the body. Figure 4 shows a section of the rocker arm 14 along line B-B of figure 3 illustrating more clearly the spatial relationship between the bore 52 in the rocker arm body 40 and the aperture 45 of the bush 44. Figure 5 is a reduced scale sectional view along line C-C of figure 3 illustrating the narrow dimensions of the nose portion 40' of the rocker arm body 40. It will be readily appreciated from this that to laterally drill a lubricant supply channel extending from an end of said nose portion to the central bore of the rocker arm body would be difficult, particularly in view of the relative narrowness of such a channel to its length and in view of the fact that the rocker arm body is normally cast or forged from metal. A previous solution to the problem of providing lubrication to the contact formed between the nose portion 40' and a valve stem assembly 46 has been to include such a channel but this resulted in the discarding of a significant proportion of machined rocker arms due to machining difficulties. Figure 6 is a side sectional view of an upper portion of an engine illustrating a rocker arm lubrication arrangement in accordance with the present invention. It can be seen from figure 6 that a rocker arm 14 is supported by a support shaft 12 at a position just below an engine cover 60 whereby a nose portion 40' of the rocker arm 14 contacts a valve stem assembly 46 whilst, at its other end, an adjusting screw bottom end contacts with a cup-shaped upper end of an engine push rod 62. In use, an upward movement of the push rod 62 causes pivotal movement of the rocker arm 14 about the shaft 12 causing the nose portion 40' to act against the valve stem assembly 46 urging it against a return spring means 64 to a depressed position. As the push rod 62 drops, the valve stem assembly 46 is returned to its original position by the urging force of the compressed return spring means 64 and in turn this causes the rocker arm 14 to return to its original pivotal position relative to the support shaft as illustrated by the broken outline of the nose portion in the figure. The rocker arm shown is one of a number (not shown) supported on the shaft and enclosed by the engine cover 60. The engine cover has a groove 66 around its periphery which sealingly fits upon a tongue member 68 attached to a periphery of a housing 70 for the engine. Lubrication of the ball joint formed between the lower end of the adjusting screw 48 and the upper end of the push rod 62 and of the contact between the nose portion 40' of the rocker arm body and valve stem assembly 46 can be by means of a lubricant mist generated in a lower region (not shown) of the engine whereby the rising mist coats the components of the engine lubricating their surfaces of contact. However, it has been found in some engines that the ball joints, in particular, may remain dry and this can lead to excessive wear of both the upper end of the push rods and lower ends of the adjusting screws requiring frequent adjustment or even replacement of parts. In order to overcome this problem, the rocker arms 14 are mounted upon the support shaft 12 such that their upwardly directed bores 52 can communicate with one of the upwardly directed bores 34 formed in the shaft 12. In fact, the upwardly directed bores 34 and downwardly directed bores 32 of the shaft 12 are generally formed in opposing pairs at positions along the shaft at which it is intended to locate a rocker arm 14. In use, the downwardly directed hole supplies lubricant in the form of engine oil to lubricate the contact between the rocker arm bush 44 (better seen in figure 7) and the shaft. In use, oil is supplied to the longitudinally extending bore 30 of the shaft 12 and passes through an upwardly directed bore 34 in said shaft 12 to rise through a corresponding aperture 45 in the rocker arm bush 44 and an upwardly directed bore 52 in the rocker arm body. An upper portion of each of the upwardly directed bores of the support shaft are formed of a narrower diameter. This can be achieved by a drilling process only or by firstly drilling a bore and then fitting a sleeve (not shown) within the bore. Oil supplied under engine oil pressure exits said upwardly directed bores as jets which, after rising through the rocker arm body, impinge upon an underside of the engine cover 60 to be returned back as a spray which lubricates the ball joints and nose portion/valve stem assembly contacts. However, it is preferable that the jets of oil exiting from the upwardly directed supply bores in the support shaft are not continuous since this can lead to a drop in engine oil pressure thus requiring a larger oil pump. In addition, by limiting the period of the oil jets, there is a reduction in the amount of oil required to be supplied to this part of the engine. The above feature of the invention can be achieved by dimensioning the respective bores (34,52) in the support shaft 12 and rocker arm body 40 such that during a pivotal movement of the rocker arm said bores become radially displaced closing over the upwardly extending bores in the support shaft. This is better illustrated in figure 7 which shows an enlarged view of the revealed portion figure 6 illustrating the relative rotated position of the rocker arm body 40 to the shaft 12 at a point where further rotation of the rocker arm body 40 in the direction of arrow D will cause the upwardly directed bore 34 of the shaft 12 to be closed off. Pivotal movement of the rocker arms 14 relates directly to the reciprocal motion of the push rod which takes its motion from the engine camshaft (not shown) which in turn relates to crankshaft rotation. It is envisaged that the relative dimension of the bores in the rocker arm bodies to the upwardly directed bores in the support shaft should be such that the period of each oil jet relates to 45° of crankshaft rotation. It is believed that this is suitable to provide sufficient lubrication of the rocker arm assembly contacts. However, it will be appreciated that these dimensions can be varied to provide different timed periods for the oil jets. The jets of oil impinge upon an underside of the engine cover 60 to be returned as a spray for lubricating the rocker arm assembly components. To assist the pattern of spray, there is provided a deflector member 72 on the underside of the engine cover 60 against which the jets of oil impinge. The shape of the deflection member 72 is such that it controls the spread of spray, as illustrated in broken outline in figure 6, to that best suited to the dimensions of the rocker arms 14. In one particular embodiment, this member 72 has a convex outer surface but it is envisaged that different shapes might suit different dimensional considerations. The deflection member 72 may extend along the underside of the engine cover for a length corresponding to the span between the outermost rocker arms 14. Alternatively, the deflection member may be formed of a number of portions positioned at appropriate points on the underside of the cover member for deflecting the respective jets of oil exiting from the rocker arms 14.

Claims: A rocker arm lubrication arrangement comprising a rocker arm assembly (10) consisting of a number of rocker arms (14) mounted for pivotal movement about a longitudinally extending support shaft (12) formed with a longitudinally extending lubricant supply bore (30) and a number of radially upwardly extending lubricant supply bores (34) communicating therewith, wherein at least one of said radially upwardly extending bores (34) communicates with an upwardly extending lubricant supply bore (52) in a corresponding one of said rocker arms (14) such that lubricant passing under pressure through said longitudinally extending supply bore (30) to said upwardly extending supply bore (34) forms a jet of lubricant which rises through the corresponding bore (52) in the rocker arm (14) to impinge upon an underside of an engine cover (60) and to be directed to lubricate a contact between an end of the rocker arm (40') and an engine component (46), characterised in that said at least one of said radially upwardly extending bores (34) in the support shaft (12) extends radially substantially vertically such that the jet of lubricant rises substantially vertically through the corresponding bore (52) in the rocker arm (14) to impinge upon the underside of the engine cover (60) to be returned as a spray to lubricate contacts between opposed ends (40',40") of the rocker arm (14) and corresponding engine components (46,62). A rocker arm lubrication arrangement as claimed in claim 1, characterised in that each substantially vertically extending supply bore (34) in the support shaft (12) has a portion of narrower diameter than the longitudinally extending supply bore (30). A rocker arm lubrication arrangement as claimed in claim 1 or claim 2, characterised in that at least one deflector member (72) is formed integrally with or attached to the underside of the engine cover (60) to direct said spray. A rocker arm lubrication arrangement as claimed in any one of claims 1 to 3, characterised in that pivotal movement of the rocker arm (14) causes the corresponding rocker arm supply bore (52) to become radially displaced relative to the radially substantially vertically extending supply bore (34) to the extent of cutting off lubricant flow for a portion of a period of oscillation of pivotal movement of said rocker arm (14). A method of lubricating a rocker arm assembly comprising: providing an internal combustion engine including a rocker arm support shaft (12), a number of rocker arms (14) pivotally mounted on the rocker arm support shaft (12), and an engine cover (60) located above the rocker arm support shaft (12) and the rocker arm (14); supplying lubricant under pressure along a longitudinally extending bore (30) formed in the rocker arm support shaft (12) ; diverting the lubricant upwardly through a number of radially upwardly extending bores (34) in the shaft (12) and corresponding bores (52) in the rocker arms (14) to thereby form a jet of lubricant; impinging said lubricant jet on an underside of the engine cover (60) to direct said lubricant to lubricate a contact between an end (40') of the rocker arm (14) and an engine component (46); the method being characterised in that the support shaft (12) is arranged in the engine such that the upwardly extending bores (34) in the support shaft (12) are directed to extend radially substantially vertically and the jet of lubricant rises substantially vertically through the substantially vertically extending bores (34) and the corresponding bores (52) in the rocker arms (14) to impinge on the underside of the engine cover (60) to be returned as a spray to lubricate contacts between opposed ends (40',40") of the rocker arm (14) and corresponding engine components (46,62). A method as claimed in claim 5, characterised in that it includes the step of directing the jet of lubricant such that it impinges on a deflector member (72) located on the underside of the engine cover (60). An engine cover for an internal combustion engine, said cover being arranged to locate, in use, on an engine above a rocker arm assembly (10) comprising a rocker arm support shaft (12) and a number of rocker arms (14) pivotally mounted on the shaft (12), said engine cover (60) including a deflector member (72) configured to receive a jet of lubricant rising out of a supply bore (52) formed in the rocker arms (14) and to direct said lubricant to lubricate a contact between an end (40') of the rocker arms (14) and a corresponding engine component (46), characterised in that the deflector member (72) is positioned on said engine cover (60) such that, in use, it locates at a position generally vertically above the rocker arm bore (52) and it is configured to return the jet of lubricant as a spray for lubricating opposed ends (40',40") of the rocker arms (14) and corresponding engine components (46,62). An engine cover as claimed in claim 7, characterised in that the deflector member (72) is integrally formed with the underside of said cover (60). An engine cover as claimed in claim 7 or claim 8, characterised in that an outward facing surface of the deflector member (71) which receives the jet of lubricant is concave. An engine cover as claimed in any one of claims 7 to 9, characterised in that the deflector member (72) extends the full length of the cover member (60). An engine cover as claimed in any one of claims 7 to 9, characterised in that the deflector member (72) comprises a number of deflector member portions each located on the underside of the cover member (60) at a position generally vertically above a respective rocker arm (14).

Inventors: JONES DEREK, JONES, DEREK
Applicants: PERKINS LTD, PERKINS LIMITED
Application year: 1994
Main classification: F01L1
IPC codes: F01M9, F01L1, F01M1